begin.start
package begin;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import resource.getresource;
import begin.enter;
public class start extends JFrame {
public static void setButton(final int k,String s,final JFrame jf,final Container cont) {
getresource get = new getresource();
JButton jb = new JButton(s,get.geticon("button/button1.bmp"));
cont.add(jb);
jb.setBounds(100,50*k+5,200,40);
jb.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
jf.dispose();
enter en = new enter();
en.entermain(k);
}
});
jb.setSize(200,40);
}
public static void main(String[] args) {
JFrame jf = new JFrame("开始游戏");
String str[] = {"","简单","普通","困难","疯狂","超神" };
Container cont = jf.getContentPane();
cont.setBackground(Color.orange);
cont.setLayout(null);
jf.setVisible(true);
jf.setBounds(434,219,400,330);
jf.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
JLabel jl = new JLabel("请选择难度：");
cont.add(jl);
jl.setBounds(100,5,200,40);
for (int i=1; i<6; i++) {
setButton(i,str[i],jf,cont);
}
}
}

begin.enter
package begin;
import course.main;
public class enter {
public void entermain(int k) {
int arr[][] = {{0,0,0},{0,3,5},{0,4,6},{0,5,7},{0,6,8},{0,7,9}};
main m = new main();
m.mainwindow(arr[k][1],arr[k][2]);
}
}

course.main
package course;
import java.awt.*;
import java.net.*;
import javax.swing.*;
import resource.getresource;
public class main extends JFrame{
public void mainwindow(int colornum,int ballnum) {
JFrame jf = new JFrame("泡泡龙II");
Container cont = jf.getContentPane();
jf.setVisible(true);
jf.setBounds(184,69,900,630);
jf.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
add(new paintimage());
}
class paintimage extends Canvas {
public void paint(Graphics g) {
this.paint(g);
Graphics2D g2 = (Graphics2D)g;
g2.drawImage(new getresource().getimg("background/mainwindow.bmp"),0,0,this);
}
}
}

resource.getresource
package resource;
import java.awt.*;
import java.net.*;
import javax.swing.*;
public class getresource {
public URL geturl(String s) {
URL url = getresource.class.getResource(s);
return url;
}
public Icon geticon(String s) {
String ur = System.getProperty("user.dir")+"/src/resource/"+s;
Icon icon = new ImageIcon(ur);
return icon;
}
public Image getimg(String s) {
String ur = System.getProperty("user.dir")+"/src/resource/"+s;
Image img = Toolkit.getDefaultToolkit().getImage(ur);
return img;
}
}

两张图片，分别是
resource/button/button1.bmp
resource/background/mainwindow.bmp

顶起

再次顶起

又一次顶起